State officials said surging demand, driven by people trying to keep their homes warm, and cold weather knocking some power stations offline had pushed Texas' system beyond the limits.
“This event was well beyond the design parameters for a typical, or even an extreme, Texas winter that you would normally plan for.
At DFW, the temperature was 4 degrees Fahrenheit (-15 degrees Celsius) — 3 degrees (-16 degrees) colder than Moscow.
In Houston, officials said Bush Intercontinental Airport runways would remain closed until at least 1 p.m. Tuesday, a day longer than previously expected.
The southern Plains had been gearing up for the winter weather for the better part of the weekend.